Gear grinding and lapping machine



w. ROSS 2,482,800

GEAR GRINDING AND LAPPING MACHINE 4 Sheets-Sheet 1 Sept. 27, 1949.

Filed April 8, 1946 INVENTOR. V v Whe -5%. BY

Sept. 27, 1949. w. F. ROSS 2,482,800

GEAR GRINDING AND LAPPING NACHINE Filed April 8. 1946 4 Sheets-Sheet 2 IN VEN TOR.

Sept. 27, 1949. w. F. ROSS em eamnnze m urrm means 4 Sheets-Sheet 3 Filed April 8, 1946 4 m m mlln hh J M 5 M m w v w J J ln W I. W a v I w x 1 I Sept. 27, 1949. oss 2,482,800

GEAR GRINDING AND LAPPING MACHINE Filed April 8, 1946 4 Sheets-Sheet 4 i [I A V Patented Sept. 27, 1949 UNITED STATES PATENT OFFICE en i- Niles-Dement- Company, West Hartford, Conn., a corporation of New Jersey Application April 8, 1946, Serial No. 660,349

2 Claims- (Cl. 51-45) The present invention relates to automatic gear grinding machines, and more particularly to a gear grinding machine for finishing spur and helical gears.

The primary object of the invention, is to pro vide a continuously operating machine which can be easily adjusted for cutting helical gears of various sizes and dimensions as well as different helix angles without recourse to change speed or specially provided gearing to compensate for the helix angles of the gears.

Another object of the invention is to provide a machine tool for grinding and finishing spur and helical gears by employing a grinding wheel or the threaded type having a helical groove of predetermined pitch formed in its periphery for grinding and finishing gears and gear blanks of r a similar pitch.

Another object of the invention resides in the provision of a work supporting arbor which is rotated at definite predetermined speeds whereby the work piece will follow the feed of the threaded grinding wheel to produce a finished gear of similar pitch with the teeth of the gear extending at a predetermined lead angle.

Still another object of the invention is to provide a machine tool of the above mentioned character in which the grinding wheel or work support are relatively moved under controlled speeds and to provide suitable mechanism for producing such controlled speed movements as to enable the use of the complete peripheral area of the grinding wheel during a grinding cycle.

A further object of the invention is to provide a machine of the above mentioned type in which the threaded grinding wheel is rotated at a rate of speed to give the correct peripheral grinding speed and the work or gear supporting arbor is rotated at theproper rate of speed for the number of teeth in the particular gear being ground.

Another object of the invention is to provide a machine of the above mentioned character in which the threaded wheelis moved axially in a direction at right or oblique anglesto the axis of the work supporting arbor so as to utilize the entire peripheral face of the grinding I wheel. 7

Another object oi the invention is to provide a gear grinding and machine of the above mentioned character in. which the threaded grinding wheel may be rotated at various speeds wheel to utilize the entire peripheral area. thereof.

A still further object of the invention is to provide a gear grinding and finishing machine in which the work or gear supporting arbor is hydraulically moved axially as well as laterally to provide for feed movement of the gear blank relative to the grinding wheel and also a movement of the work or gear blank past the grinding wheel so that a higher degree of accuracy can be ob tained in the finished gear.

It is also an object of the invention to provide a gear grinding and finishing machine of the above mentioned character in which the gear or work supporting arbor may be manually fed toward and away from the threaded grinding wheel independently of the hydraulic or mechanical feed movement so that the correct depth of cut may be obtained on the finished gear.

The invention also contemplates the provision of a gear grinding and finishing machine in which the gear supporting arbor is rotated at a predetermined speed and is manually given an inieed and a tangential pass teed relative to the threaded grinding wheel by automatic means to produce controlled sequential movement of the work piece or gear blank during each grinding cycle; the provision of a machine tool for grinding and finishing either spur or helical gears and to provide automatic control mechanism for eilecting the various controlled movements of the threaded grinding wheel as well as the infeed and tangential pass feed of the wok piece relative to the threaded grinding wheel; and the provision of a. machine tool for grinding and finishing gear blanks in which the work support or gear blank arbor ma be moved along a path normal to the axis of rotation of the grinding wheel and rotated at a different speed to compensate for the sliding movement of the gear blank supporting arbor when the grinding wheel is rotated at a predetermined speed without axial movement.

Other objects and advantages of the invention will become apparent as the invention is further described, by way of example, in and by the following description of the machine shown in the slightly greater or less than the normal speed thereof to facilitate grinding and finishing helical gear blanks, thus compensating for the axial accompanying drawings, wherein:

- Figure 1 is an elevation of the upperrpart of a gear grinding machine embodying the said invention, with the work table tilted for the grinding of a helical gear;

Figure 2 is a vertical transverse section of the frame structure and work table supporting elements, said section being taken on a plane sub- 3 stantially passing through the axis of the grinding wheel spindle;

Figure 3 is a vertical section through the gear box of the grinding wheel spindle, taken on the same plane; and

Figure 4 is a cross section through the said gear box, taken on a plane indicated by the line 4-4 in Figure 3.

While Figures 3 and 4 are drawn to the same scale, Figures 1 and 2 are drawn to different and smaller scales for convenience. Similar characters of reference indicate similar parts in the several figures of the drawings.

II] indicates the frame structure of the machine housing a gear box II surmounted by the tubular quill housing I2, and I3 indicates a gear-grinding abrasive wheel, which will be later referred to in greater detail, said wheel being mounted on the upper end of vertical spindle I4 coaxial with the said quill housing I2.

Mounted on arcuate ways I5 of a longitudinally movable feed table 30 is a tiltable work table I6 adjustable as to angle of tilt by the adjusting worm II, this work table I6 being' capable of rotation about an axis transverse of the axis of the work and perpendicular to the axis of the aforesaid abrasive wheel spindle I4. The said table I6 is also provided with a cross slide I8 carrying the centers I9 and 20 between which centers the work arbor 2| is held. 22 indicates the work in the form of a gear blank to be ground by the said abrasive wheel I3.

In Figure 1 the axis of this gear blank 22 is shown as being tilted, by corresponding adjustment of the tiltable table I6, and so positioned that the helical teeth to be ground thereon are presented in true parallelism with the lead angle of the thread previously formed an the periphery of the abrasive wheel I3. It should be noted that the dotted representation of teeth, on the blank 22 as shown in Figure 1, indicate those teeth which are directed toward the abrasive wheel and consequently on the back of the said gear blank 22 as viewed in the said Figure 1.

23 indicates a receiving Selsyn-type motor arranged to drive the work arbor 2I through the medium of a headstock 24, this'receiving Selsyn being electrically connected for synchronized operation by a sending Selsyn-type motor 3I later referred to. The headstock 24 is in the form of a gear box housing change speed gears (not shown) for varying the rotational speed of the work,

Manual movementof the cross slide I8 of the work table is effected by the hand wheel 25, the spindle 26 of which has a splined connection with the cross slide feed screw 21, the opposite end of the said feed screw being connected to the plunger 28 of a hydraulic cylinder 29 for power operation of the said cross slide, as will be further referred to hereinafter.

Thus, during a grinding operation on the blank 22, the said blank will be rotated by the receiving selsyn-type motor 23, which latter motorv is operated from spindle I4 of the abrasive wheel I3 through the sending Selsyn motor 3|.

The co-ordinated rotational speeds of the sending and receiving Selsyn-type motors are intended to insure the proper relative rotational speed of the work to that of the abrasive wheel as required by the number of teeth to be ground on the blank.

In order that the teeth being cut on the blank 22 will be properly presented to the threaded groove on the periphery of the said abrasive wheel, as such thread advances in accordance with its pitch during the rotation of the said wheel, additional rotation is superimposed upon the normal rotation, called for by the pitch of the thread of the abrasive wheel and to compensate for axial movement of the abrasive wheel which is provided for in one direction; and a corresponding rotation is subtracted from such normal rotation of the wheel to compensate for axial movement of the said abrasive wheel in the opposite direction. The mechanism providing this compensation will be explained hereinafter.

Power for these axial movements of the abrasive wheel I3 is obtained initially from a hydraulic motor 32, through suitable gearing 33, shaft 34, worm 35, and worm wheel 36; the latter being mounted on the casing or spider 31 of a differential journalled within the aforesaid gear box II. 38 and 39 are upper and lower gears of the said differential, 40 being the pinion mounted on the housing of spider 31. l

The upper gear 38 of the said differential has a splined connection with the lower end of the abrasive wheel spindle I4, as clearly seen in Figure 3, to permit vertical movement of the said spindle I4 while it is being driven through the said differential gear by means of the pulley 44 mounted on the lower end of the shaft 45 of the gear 39. Any suitable motor (not shown) may be provided to drive this pulley 44.

In the upper end of the said gear box II is a further helical gear '4I, driven by a pinion 42 mounted on the shaft 43, which shaft receives its power from the shaft 34 through the medium of change speed gears 46,41, 48, 49, 50, and 5I.

, The opposite end of this shaft 34 is intended to be connected to suitable limit control switches (not shown) for timing the starting, stopping, or reversing operations of the pumps or motors controlling the operation of the plunger 52 of the hydraulic longitudinal table feed cylinder 53 and for controlling the operation of the hydraulic cross feed cylinder 29 of the said work table to produce the timed relative. movements of the parts hereinafter explained in describing the operation of the machine. The construction and operation of such limit switches being well known and in considerable variety of design, and such construction not being an essential feature of the said invention, specific illustrations or descriptions thereof are not entered herein. As an indication of a general arrangement of controls, however, the schematic showing in broken lines in Figures 1, 2 and 4 may be noted wherein the hydraulic motor 32 is shown asbeing controlled in its operation by a belt-driven variable delivery pump I32. The shaft 43 is also shown as being provided with a worm I43 geared to a worm wheel I 44 provided with limit switches I45, I46 and I41, the limit switch I 45 being positioned for actuation upon the completion of the return of the gear wheel to the limit'of its downward reciprocal stroke, and switch, I41 positioned to control the amount of grinding wheel rise on its upward stroke and thereby start the wheel on its return or downward stroke. The limit switch I48 is positioned to control the table feed, which in Figure 1 is shown as being provided with a limit switch I48 for controllin reverse tangential feed and a limit switch I49 for controlling the forward tangential feed;

I50 and I5I representing the usual adjustable stops or contacts such as are well known in connection with limit switches of this nature.

Referring to Figure 2, the shaft 28 of the hydraulic cylinder 29 operating the cross slide is indicated as being provided with a plunger I28 for 3i, and also with a bevel gear 60 adapted although the through the said lowering of the quill 55, with slidablein the quill housing I! and supported on a nut. 55, which nut is in threaded engagement with the tubular quill screw 51 extending upwardly from the quill gear II. The rotary and reciprocal spindle M of the abrasive wheel passes axially tubular quill screw 51. Obviously, rotation of the quill gear ll in one or the other directionby the pinion 42 will effect'the raising or consequent raising or lowering of the abrasive wheel 13 and its spindie It as permitted by the splined connection of the said spindle with the shaft of the upper differential gear 38.

The shaft 45 of the lower differential gear 39,

which shaft may be considered as the lower extension of the abrasive-wheel spindle it, carries the bevel gear 58 which meshes with the bevel gear drive 59 of the sending Selsyn-type motor the rotation of which is controlled by a, solenoid brake may be of any well-known commercial type and is therefore not illustrated in detail.

The operation of the machine will now be-described as applied to the forming or grinding of a helical gear, for which work it is peculiarly ular spur gears may be readily eilected on the machine as will be readily apparent.

I motor 32 isshut oil or otherwise rendered inoperative to the extent that the shaft 34, best seen in Figure 4, is not being rotated, that the solenoid brake Si is released, and that a speed of, say, for the sake of example only, 1275 R. P. M., is being imparted by a suitable source of power to the pulley 44; so, that, as the differential casing 31 is held from rotating by the stationary worm wheel 35, these revolutions will be transmitted through the differential gears 39, ill, and 38 directly to the grinding wheel spindle grinding wheel l3 also a speed of 1275 R. P. M. This, being the speed at which the thread formed on the periphery of the abrasive wheel will rotate in contact with the work, to produce teeth thereon by a continuous grinding action, gives us approximately six thousand feet per minute on the periphery of the said abrasive wheel.

At the same time the bevel gears 58 and 59 rotate the armature of the sending Selsyn unit 3 i at this same 1275 R. P. M., which, due to electrical coupling with the receiving Selsyn unit 23, imparts a corresponding i275 R. P. M. to the said receiving unit 23.

The receiving Selsyn, however,-must effect rotation of the work at a speed commensurate with the pitch diameter oi the work as related to the rotation of the threaded abrasive wheel i3, as will be well understood, so that selection of gear change within the headstock 24 is resorted to to provide a rotation of the.work which will be 1275 R. P. M. divided by the number of teeth in the gear. Thus one revolution of the abrasive wheel I3 will be. accompanied by the indexing of one 8| which 6 tooth spacing on the work to be ground. However, as the rotation of tlnuous, the rotation of the work is continuous, v

It is to be further understood that when the threaded abrasive wheel and thework blank are 1 brought into mesh, while being correspondingly wheel arbor 54, attached tothe rotated, the rack form of the thread of theabrasive wheel will grind by the conjugate method the tooth form desired on the periphery of the blank, the said blank being moved tangentially across the face of the abrasive'wheel by the longitudi-v nal feed of the work table as the grinding pro-Y grosses.

The longitudinal f of the work table is. effected by the reciprocal action of the plunger 52, of the hydraulic cylinder 53; and the movement of gear blank 22 into mesh with the thread of the abrasive wheel I3 is controlled by the plunger 28 of the hydraulic cylinder 29, shown in Figure 2, whereupon the finer feed of the work into the said abrasive wheel is manually eifected by operation of the hand wheel 25 to secure accurate depth of cut as desired. Any suitable micrometer adjustment of the said hand wheel provided for determining the extent of such adjustment, Suitable control of the length of the forming or grinding of regof the gear blank tangentially of the longitudinal feed will determine movement of the abrasive wheel to take care of gear blanks of varying face stroke of the plunger hydraulic cylinder 53 widths.

Provision is made for moving the abrasive wheel i3 axially, up and down, so that substantially the entire face of the wheel may be utilized in the gear grinding operation. It should be noted that such utilization of more than a single point on the face of the grinding wheel has been heretofore accomplished by grinding the work in 40 Let it be assumed for the moment that the fluid one given position and then movingthe work out of mesh to shift to another position,

- work is then'again brought back into mesh, even H, giving the abrasive though the movement of the work from the original position may be quite slight. However, the arrangement herein disclosed provides for a smooth continuous action between the abrasive wheel and the gear blank, being so coordinated as to continually and accuratelyoifer a new section of the threaded abrasive wheel to the gear to be ground.

In explaining such action, the general grinding cycle, for the moment ignoring vertical axial movement of the abrasive wheel, is explained as follows: Assuming themain spindle oi the abrasive wheel to'be in pure rotation, the cross feed cylinder on the work table moves the gear blank to be ground into mesh with the thread of the abrasive wheel while said abrasive wheel and the work are rotating at appropriate speeds, as previously described. Upon reaching the depth desired for grinding, the longitudinal feed cylinder will be brought into operation to cause the work to pass by the grinding wheel at a rate which will give the most desirable feed per revolution and, upon reaching the end of the longitudinal feed stroke, the cross feed cylinder will be energized bysuitable timing mechanism provided to move the work out from the abrasive wheel. Then a rapid return may be given to the work table, the work again moved into grinding position by the cross feed hydraulic cylinder, and the cycle repeated as many times as is required, with manual operation of the cross feed to bring the work into closer mesh, with each cycle, until the required amount of stock has been removed.

Having now described a conventional grinding the abrasive wheel is conaccordingly,

may be I when the -to the control of axial motions of the abrasive.

wheel, and the superimposing of an additional slight -rotary motion upon the normal rotation of the said abrasive wheel.

As previously stated, we are'assuming the normal rotation of thisabrasive wheel to be 1275 R. P. M., so that, if we now rotate the shaft 34 a sumcient number of times to cause the outer gear or pinion 4. of the diflerential to make half a revolution about the axis of the gear 39 in the space of one minute, this will resolve itself into one additional revolution of the output gear 38, thus giving to the said output gear 38 and to the abrasive wheel a new speed of 1276 R. P. M.

It should be further noted that, in introduce ing the required revolutions to the shaft 34 to produce this result on the speed of the abrasive wheel, we cause the change gears 46, 41, 48, 45, i0, and ii to rotate the shaft 43 so that, during this minute referred to, the rotation of such shaft 43 with its worm 42 will rotate the gear 4| and quill screw 31 to an extent calculated to move-the quill 55 (and consequently the abrasive wheel) axially through one lead of the abrasive wheel thread in the same minute.

Thus, there has been superimposed on the normal speed of theabrasive wheel a full revolution which automatically compensates for the vertical displacement of the .thread of the grinding wheel so that the actual mesh relationship between the thread of the grinding wheel and a tooth on the work has been maintained, notwithstanding the axial movement of the said abrasive wheel.

Having determined the time required for the gear blank face width to pass by the center line of the abrasive wheel in order that a tooth may be defined entirely across the face of the blank, it is required that the amount of rotation of the shaft 34 should also be determined in order that the abrasive wheel will move axially upward to the required extent, in that same length of time, in order that the entire working face of the said abrasive wheel may be brought into use. This determination of the amount of rotation which must be imparted to the said shaft 34 may be arrived at by the use of a suitable tachometer which may be built into the machine as part of a control panel (not shown).

Assuming that at this time, prior to commencing any grinding operation, the abrasive wheel spindle has been running at a rate of 1275 R. P. M., it will follow that, by now rotating the shaft 34 at a speed which has been determined, the abrasive wheel starts to rise upwardly during such rotation by virtue of the simultaneous operation of the quill screw 51 from the shaft 43; and, for every lead of the thread on the said abrasive wheel l3 it so moves upwardly, the regulated speed of the shaft 34 will cause the pinion 4! of the differential to add one revolution to the speed of the abrasive wheel l3.

Upon the movement upwardly of the said abrasive wheel,say A inch, a suitably set limit switch,

which may be operated by the shaft 43 as previously stated, will be contacted to cause the cross feed cylinder 25 to operate and move the work table into grinding position. Upon reaching the in position, the limit switch means will cause the longitudinal work table cylinder 53 to receive a flow of oil under control to cause the gear blank to feed past the abrasive wheel at a predetermined rate; it being home in mind that, while this feeding pass is being efiected, the abrasive of its threaded grinding surface to the teeth which are being ground on the work.

Upon. reaching a predetermined setting, the work table is moved longitudinally a little over 4 inches to complete a grinding pass, by which time the abrasive wheel II has almost reached the top of its vertical stroke. The cross feed'table, under the influence of suitab y provided limit switches. now is ,moved outwardly away from the abrasive wheel by operation of the hydraulic cylinder 29, and further limit switchesthen cause the longitudinal feed cylinder II to receive a large flow of oil for a return-stroke operation, at a rapid rate, of the feed table to its starting position while the work is free of the abrasive wheel.

During all this, of course. the direction of the rotation ofthe'said abrasive wheel is maintained and does not change throughout the entire cycles of grinding operation (as is the speed and direction of rotation of the work blank), but between each cycle the said abrasive wheel is must be lowered to its original position, which is effected by limit switch control of the fluid motor 32 to re- U verse the direction of rotation ofthe shaft 34 to such' an extent that the pinion 40 of the dinerential will be moved around the axis of the input gear 33 thereof in a reverse direction to that previously described, whereby it will now subtract one revolution from the normal 1275 R. P. M. of the output gear 38 of the diiferential and therefore of the abrasive wheel it.

At the same time, the direction of rotation of the shaft 43 will likewise be reversed, as will the directionof rotation of the quill screw 51 causing the quill I5 to move downwardly in its housing and so lower the abrasive wheel. During this lowering operation, the rotary speed of the abrasive wheel has been reduced to 1274 R. P. M. by the described action of the differential; so that the thread of the periphery of the abrasive wheel may be considered performing an unwinding function. during the lowering of the said abrasive wheel. Consequently, as the abrasive wheel is returned to its lower position ready for resumption of the next pass of the work, the truemeshing relationship of the thread on the abrasive wheel to the teeth being ground on the work is accurately maintained.

So far. the operation of the device has been described simply as in the grinding of spur gears, but an important feature of the machine is the provision for grinding helical gears without calling for the use of a special set of change gears and a lead screw to compensate for the helix angle of the teeth to be ground, or for the use of special guides or other conventional means such as have been heretofore required in gear grinding machines of this general type, wherein it has been necessary to superimpose rotation on the helical gear blank in order to develop a lead on the said gear blank.

The present invention is characterized by the use of a threaded abrasive wheel while taking advantage of its conjugate action to arriveat a means of grinding helical gears wherein they are treated precisely as are spur gears.

It should be noted that the mean helix 'angle of the threaded abrasive wheel is built into the relationship or the longitudinal ways of the work table and the center line of the said wheel, whereby the relative helix angles of any helical gear is set directly.

In the grinding of a spur gear, the work table trunnion is always set at a zero reading so that the thread at the abrasive wheel lies along the center lineof a helical gear, if unwrapped or developed into a flat plane, arev actually straight parallel lines similar to those of a spur gear and have no lead, but are merely characterized by the angular displacement of the teeth in relation to a fixed line at rightangles thereto, Consequently, in the lilustrated machln all that is required is to rotate the trunnion work table l6, by means of the worm H, to an angle which is equivalent to the helix angle of the gear to be ground, thereby setting the center line of the teethof the helical gear in the same plane for grinding as would be the case with spur gears, and then longitudinally feeding the table along that line while the abrasive wheel performs the motions which have been described above.

the gears space. Now the teeth of tinucusly rotating, and means for moving the gear blank tangentially with respect to the grindi118 wheel.

4.Amachinetool for grindingandfinishing gear blanks, comprising a threaded-grinding wheel for conjugate coaction with agear blank to be ground, means for relatively moving the gear blank and grinding wheel with respect to For a given face width of the gear blank the working stroke will, however, be longer due to the greater length of the helical teeth, and this, of course, is taken into consideration in setting the limit switches controlling longitudinal feed of the work table. Limitation of face widths of high helix gears depends on the width of abrasive wheel face and length of travel, and within reason of design limitations, such as that illustrated, something like 99% of the helical gears which are of generally narrow face widths may be ground by the means and in the manner herein outlined. The operation of the abrasive wheel is exactly the same as described in connection with grinding of spur gears, the helical gear being treated as a spur gear, and all the usual conventional methods of obtaining spiral and lead feed on the work are dispensed with, utilizing the conjugate action of the threaded abrasive wheel and the continuous rolling action of the spiral gear blank to be ground.

What I claim is:

1. A machine tool for grinding and finishing gear blanks, comprising a threaded grinding wheel for conjugate coaction with a gear blank to be ground, means to axially move said wheel, means for relatively moving the gear blank and grinding wheel with respect to one another during the grinding operation, and means for varying the speed of angular displacement of the grinding wheel while both grinding wheel and gear blank are continuously rotating to compensate for said axial movement of said wheel.

2. A machine tool for grinding and finishing gear blanks, comprising a threaded grinding wheel for conjugate coaction with a gear blank to be ground, means to axially move said wheel, means for relatively moving the gear blank and grinding wheel with respect to one another during the grinding operation, means for varying the speed of angular displacement of the grinding wheel while both grinding wheel and gear blank are continuously rotating to compensate for said axial movement of said wheel, and means for imparting an in-feed movement of said gear blank and a traversing movement laterally relative to said grinding wheel.

3. A machine tool for grinding and, finishing gear blanks, comprising a threaded grinding wheel for conjugate coaction with a gear blank to be ground, means for relatively moving the gear blank and grinding wheel axially of said wheel with respect to one another during the grinding operation, means for varying the speed of angular displacement of the grinding wheel while both grinding wheel and gear blank are conone another during the grinding operation axially of said'wheel, means for' v'arying the speed of angular displacement of the grinding wheel while both grinding wheel and gear blank are continuously rotating, means for imparting an in-feed movement of said gear blank relative to said grinding wheel, means for moving the gear blank tangentially with respect to the grinding wheel, and means for controlling said in-feed and tangential feed so that the gear blank will-move in a cycle to provide a tangential pass feed relative tosaid grinding wheel. j

5. A machine tool for and 'finishing gearblanks, comprising a threaded grinding wheel for conjugate coaction with a'g'ear blank to be ground, means for relatively moving the gear blank and grinding wheel axially with respect to one another tion, means for varyingthespeed of angular displacement of the grinding wheel while both grinding wheel and gear blank are continuously rotating to compensate for said axial movement, and means for varying theangle of the axis of rotation of said gear blank with respect to the axis of rotation of the grindin wheel to facilitate the grinding and finishing of helical gears.

6. An automatic machine tool for grinding and finishing gear blanks, comprising a threaded grinding wheel adapted for conjugate gear grinding, a gear blank supporting arbor-disposed tangentially with respect to the peripheral surface of said grinding wheel, means for driving the arbor and grinding wheel at a'rate of speed'such that the thread on the grinding wheel will mesh with the teeth on the. gearblank,- means for axially reciprocating the grinding wheel, variable speed means for effecting timed up and down movement of said grinding wheel to compensate for variations of pitch relationship, means for moving the gear blank toward and away from said grinding wheel, means for moving said gear blank in an axial direction tangent to said grinding wheel, and control means for automatically causing said gear blank to move into and out of engagement with said grinding wheel after said tangential movement thereof in both directions of movement.

I. An automatic machine tool for grinding and finishing gear blanks, comprising a threaded I grinding wheel adapted for conjugate gear grinding, a gear blank supporting arbor disposed tangentially with respect to the peripheral surface of said grinding wheel, means for driving the arbor and grinding wheel at a rate of speed such that the thread on the grinding wheel will mesh with the teeth on the gear blank, means for axially reciprocating the grinding wheel, means for varying the speed of the grinding wheel during such reciprocating movement thereof to compensate for variations of pitch relationship, means for moving the gear blank toward and away from said grinding wheel, means for moving said gear blank in an axial direction tangent to said grinding wheel, control means for automatically causing said gear blank to move into during the grinding operain directions of movement, and means for manually producing an in-feed of said gear blank relative to said grinding wheel to regulate the depth of cut,

8. Amachine for grinding and finishing gear blanks, comprising a machine frame, a grinding wheel spindle mounted in said frame for axial movement, a threaded grinding wheel mounted on said spindle, a machine slide movable on said frame tangentially withrespect to said grinding wheel, a cross slide mountedon said first mentioned' ;slide,, a gear I blank supporting arbor mounted on said cross slide extending in a plane tangential tosaid grinding wheel, a drive shaft for. said grinding wheel spindle, means for rotating said drive shaft and gear blank suppporting arbor at a rate of speed to normally cause conjugate coaction between the thread on the grinding'wheel and the teeth 'on said gear blank, gearing interposed between said drive shaft and grinding wheel spindle, feed means interconnecting said gearing with said grinding wheel spindle for feeding the same-axially, and means operatively associated with said machine for controlling said, slide, cross slide and gearing wherebysaid gear blank will be moved tangentially to and fro during the in and out feed thereof and said grinding wheel will be rotated at a rate of speed which will not destroy the pitch relationship between the gear blank and said threaded grinding wheel when said grinding wheel is -moved axially in a direction parallel with the plane of the axis of said grinding wheel.

9. A machine for grinding and finishing gear blanks, comprising a machine frame, a grinding wheel spindle mounted in' said frame for axial movement, a threaded grinding wheel mounted on said spindle, a machine slide movable on said frame tangentially with respect to said grinding wheel, across slide mounted on said first mentioned. slide, a gear blank supporting arbor mounted on said cross slide-extending in a plane ing the in and out 12 tangential to said grinding wheel, a drive shaft for said grinding wheel spindle, means for rotating said drive shaft and gear blank supporting arbor at a rate of speed to normally cause conjugate coaction between the thread on the grindin wheel and the teeth on said gear blank, gearing interposed between wheel spindle, feed means interconnecting said gearing with said grinding wheel spindle for feeding the same axially, and means operatively associated with said machine for controlling said slide, cross slide and searing whereby said gear blank will be moved tangentially to and fro durfeed thereof and said grinding wheel will be rotated at a rate of speed which will not destroy the pitch relationship between the gear blank and said threaded grinding wheel when said grinding wheel is moved axially in a direction parallel with the plane of the axis of said grinding ferential gear set interconnecting the drive shaft with the grinding wheel spindle such that rotation of the frame of said gear set in one direction will increase the speed of rotation of said grinding wheel and rotation in the opposite direction will decrease the speed of said grinding wheel, thus compensating for the sliding movement of said grinding wheel relative to said gear blank.

' WALTER F. ROSS.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS said drive shaft and grinding wheel, said gearing including a dif- 

